1. Field of Invention
The present invention relates to a semiconductive ceramic sintered compact that has a conductivity high enough to attain static electricity removal and antistatic purposes and has excellent mechanical properties or stability over time.
2. Background Art
Al2O3, ZrO2, SiC, Si3N4 and the like have been extensively used as structural members for semiconductor manufacturing apparatuses and liquid crystal manufacturing apparatuses by virtue of their excellent mechanical properties, abrasion resistance, and corrosion resistance. In particular, Al2O3 possesses excellent mechanical properties, abrasion resistance, and corrosion resistance and is low in cost and thus has been used in various portions of apparatuses.
An enhanced performance of semiconductor devices and liquid crystal devices in recent years has led to further microminiaturization of these devices, posing troubles of the devices caused by electrostatic discharge (ESD) that occurs in guides or the like during drive of stages in a manufacturing process. Further, static electricity should be rapidly released from around the devices. To meet this demand, ceramics, of which the surface resistivity and the volume resistivity have been lowered by adding conductive substances to alumina that is an insulator, or by using a special sintering method for static electricity removing and antistatic purposes, have hitherto been known (PTLs 1 to 4).
For example, JP 2004-099413 (PTL 4) discloses alumina ceramics that have antihalation and antistatic functions and have a specific rigidity which can maintain a large meter-size mount table with high accuracy. The ceramics include Al2O3 and three metal elements of Mn (manganese), Ti (titanium), and Fe (iron) each added in an amount of not less than 0.5% in terms of oxide to Al2O3, the total amount of the three elements being 2 to 11% in terms of oxide. As long as the present inventors know, the ceramics described in this patent publication leave room for an improvement in properties.